Wide Dynamic Range Silicon Retina with Photodiode Capacitance Modulation

Abstract

We describe an intelligent vision sensor (silicon retina) that can pre-process images in real-time by using a parallel analog circuit that mimics the structure of the neuronal circuits in vertebrate retina. In this study, we have designed and fabricated a wide dynamic range silicon retina on the basis of our previous design. The photosensor of the present chip approximates logarithmic illumination-to-voltage transfer characteristics due to a photodiode capacitance modulation technique being applied. The chip in this study has achieved a dynamic range wide enough to perceive objects in both indoor and outdoor environments. Moreover, combining the logarithmic response of the photosensor with the Laplacian-Gaussian-like spatial filtering by a resistive network makes the response amplitude of the chip independent of the illumination intensity.